An array of disk drives may be assembled to provide sufficient bandwidth to record or play digitized video signals, allowing random access to video data (tape recorders allow only sequential access). However, the data transfer rate of standard disk drives is not constant in that the disk read/write heads must often move from one track to the next and during these periods of movement, no transfer of data to or from the disk may take place. Such limitations are easily overlooked in computer applications since the computer may wait during the periods when no access is available. However, such wait periods are not appropriate in video applications given the continuous stream of data associated with a video signal. While the disks cannot support a continuous transfer data rate required for video, disk arrays are typically able to transfer data in bursts (groups of data) at rates slightly higher than the required continuous rate.
Redundant data storage may be provided to insure accurate data reproduction in case of disk drive failure. However, such redundancy can greatly increase the cost of the system when expensive disk drives are employed. Once a determination of drive failure is made, the redundant data may be retrieved, but a redundant system typically will wait a relatively long time period before determining that a drive has failed. Such waits may not be appropriate during playback of continuous data.
Another problem attendant with an array of disks is that data retrieval speed is dictated by the slowest disk in the array.